Catching a virus may not always a bad thing. Researchers have found that some viruses found on mucosal surfaces might actually protect you from disease. Find out how...

Bacteria and other pathogens often enters the body at mucosal surfaces, which
line body cavities that are exposed to the environment. Among the microbes
that take residence in these surfaces are small viruses known as
bacteriophages, which infect and kill bacteria. But the role that such
viruses play in defending their host against infection has remained
undocumented, until now.

In a new study, researchers report that some viruses bind to the mucosal surfaces of humans and many animals to provide a previously unknown antimicrobial defense for the underlying host—directly killing bacteria on these surfaces. Source: PNAS

In a new study, San Diego State University (SDSU) researchers report that
these viruses bind to the mucosal surfaces of humans and many animals and
provide a previously unknown antimicrobial defense for the underlying
host—directly killing bacteria on these surfaces.

In a paper published in the Proceedings of the National Academy of Sciences
(1), the team describes a new Bacteriophage Adherence to Mucus (BAM) model
and suggests that this phage-host relationship is one of the first examples
of a symbiotic relationship between phage and metazoan host.

“We’re kind of proposing that this is a new novel immunity that’s non-host
derived,” said Jeremy Barr, the paper’s lead author and a post-doctoral
research fellow in the lab
of SDSU biology professor Forest Rohwer. “This is to our knowledge one
of the first examples of a direct symbiosis between a phage and an animal.”

The phages stick to mucosal sites through protein manes on their capsids that
are similar to immunoglobulins. The group found that these
immunoglobulin-like proteins bind to sugar residues in the mucus so that the
phage can embed itself in the mucosal layer.

“The idea is novel and quite attractive,” said Fredrick Bushman, professor of
microbiology at the University of Pennsylvania who was not involved in the
study. “It makes sense that metazoa and phage would co-evolve so that phage
were concentrated at the same surface sites as bacteria, thereby allowing
the phage to access their prey efficiently and the host to block bacterial
infection…I bet many laboratories will design experiments to follow up on
these ideas.”

During previous studies of coral reef systems, Rohwer and his lab first
noticed a substantial increase in phage concentration on mucosal surfaces
compared to the surrounding cellular environment.

To follow-up, the team collected mucus samples from a diverse range of
systems, including coral, fish, mice, and humans. They then counted the
phage-to-bacteria ratio in the samples using fluorescent DNA stains and
epifluorescence microscopy. In their analysis, the group found an increased
phage-to-bacteria ratio on the mucosal surfaces that they sampled compared
to the surrounding environment.

“Since then, we knew this was something that was actually happening in nature,
and there was definitely an increase in all these all these really diverse
mucus,” Barr said. “That was kind of a starting point.”

Then the group used a well-known phage model system, bacteriophage T4, and
cultured cells to further test the phage’s dependence on the mucosal layers.
They compared two human lung cell populations: one that produced a mucus
layer and one that was modified to not produce a mucus layer.

After incubating the cells with Escherichia coli, the
researchers found that the phage protected the mucus-producing cells from
cell death. In contrast, cultured cells that did not have a mucosal layer
for the phage to stick to a cell death rate 3 times that of unmodified cells
after 12 hours.

The research may potentially lead to therapeutic breakthroughs in treatment
for Escherichia coli and other gastrological infections. “There’s
been a lot of these pathogenic E. coli outbreaks in the last couple
years,” said Barr. “There could definitely be a prophylactic treatment in a
phage therapy angle that we could work towards.”